Purification of anhydeous aluminium chloride containing iron



"I soluble in phosgene.

Patented June 13, 1933 SKATES PATENT orrics CARL Vi ASSIu T I. G. FAEBENINDUSTRIE AK'EIENGESELLSCHAFT, OF FRANKFORT- fiH-THE-MAIN, GER-IVIANY PURIFICATION OI ANHYDEOUS No Drawing. Application filed April 13, 1931, Se

The pres nt invention relates to the purification of anhydrous aluminium chloride containingiron.

has already been proposed to remove the iron from anhydrous aluminium chloride contain'ng iron by converting the aluminium chloride into a liquid aluminium chloride phosgene compound by means of phosgene, separating it from the undissolved ferric chloride and recovering aluminium chloride free from-iron by e aporating; off the phosgene. By this tr: ient, however, it is not always possi le to produce aluminium chlo ride free from iron compounds.

' .We have now found that practically pure aluminium chloride, in particular free from iron compounds, is obtained. when during or after the ohosgene treatment, but before decomposition of the double compound, the material. to be purified is subjected to a treatment with oxidizing agents, such as the halogens chlorine and bromine, preferably by leading in chlorine, in order to convert the iron into the trivalent form, which is in- The undissolved ferric chloride is then separated from the aluminium chloride phosgene double compound and the aluminium chloride recovered by evaporating the phosgene. A substantially con'iplete separation of aluminium chloride and iron chloride is efl'ected by reducing the ferric chloride to ferrous chloride prior to or w ile acting on the initial material with phosaene. The aluminium chloride is thus eomplet dissolved together with the ferrous c. ide, the iron bein then precipitatcd in the form of ferric chloride by oxidation. it has been found that the aluminium chloride containin5;:= iron chloride obtained for exanrnle from bauxite can only be incomple ely broug'l t into solution by treatment with phosg'ene. A considerable residue (up to 25 per cent) remains behind which in in tionto ferric chloride contains mainly alummium chloride and which probably consists of a complex salt of aluminium chloride and iron chloride which insoluble in phosp ene. l i llen the ferric chloride present is, however, first reduced to ferrous chloride, as for example by the addition of aluminium ALUMEIIIUM CHLORIDE CONTAINING IRON rial No. 529,808, and in Germany April 19, 1930.

or heavy metals such as iron, tin, Zinc, nickel or cobalt, or by means of hydrogen or stannous chloride, it is possible to bring the aluminium chloride completely into solution and to recover it in a form free from iron by precipitating the whole of the iron by oxidation to ferric chloride, separating the latter and decomposing the purified liquid double compound. In some cases the theoretical amount of oxidizing agent necessary to convert the divalentiron present into trivalent iron is suiiicient for the oxidation, but as a rule an excess of from to per cent is preferable.

The following examples will further illustrate how the said invention may be carried out in practice, but the invention is not restricted to these examples. The parts are by weight.

4000 parts of crude aluminium chloride containing 1 per cent of ferrous chloride and. from 5 to 6 per cent of ferric chloride are stirred for 15 hours in an enamelled pressure vessel with 6000 parts of liquid phosgene and 15 parts of chlorine at under a pressure of from 3 to l atmospheres, and after. cooling, the whole is pressed into a settling vessel at ordinary temperature. By siphoning oil, a clear aluminium cl'iloride-phosgene double compound practically free from iron is obtained which may be decomposed into its components in the usual manner. Phosgene gas may also be employed instead of liquid phosgene. In this case the phosgene gas is led from the bottom into towers filled with crude aluminium chloride. The iron is then precipitated from the eliiuent aluminium chloride phosgene compound by leading in chlorine. The iron is separated off. Pure aluminium chloride is obtained as a residue by heating the liquid.

about 15 hours in 6000 parts of liquid phosgene while stirring at C. under a pressure of from 3 to 4 atmospheres. The ferric chloride is reduced to ferrous chloride and the aluminium chloride is thus completely dissolved, together with the ferrous chloride. In order to precepitate the iron, 100 parts of chlorine (about 25 per cent excess) are led in and the whole is stirred for a short time. After cooling to 15 0., the separated iron chloride is allowed to settle. After removing it, 9800 parts of an aluminium chloride phosgene double compound practically free from iron are obtained. The aluminium chloride obtained by distilling off the phosgene contains only 0.062 per cent of ferric chloride.

If, in the process described in the first par agraph of this example, no coarse aluminium powder is added as a reducing agent, only 6200 parts of clear, iron-free phosgene double compound are obtained after sedimentation and siphoning off. In the residual sludge there are still 720 parts of aluminium chloride and 180 parts of ferric chloride.

Vhat we claim is 1. A process for the purification of anhydrous aluminium chloride containing iron compounds which comprises acting on the aluminium chloride with phosgene converting thereby the aluminium chloride into a liquid double compound, acting on the said double compound with an oxidizing agent, separating said compound from undissolved iron compounds and recovering aluminium chloride by evaporating off the phosgene.

2. A process for the purification of anhydrous aluminium chloride containing iron compounds which comprises acting on the aluminium chloride with phosgene convert- Ting thereby the aluminium chloride into a liquid double compound, acting on the said double compound with chlorine, separating said compound from undissolved iron compounds and recovering aluminium chloride by evaporating off the phosgene.

3. A process for the purification of anhydrous aluminium chloride containing iron compounds comprising ferric chloride which comprises reducing the ferric chloride present to ferrous chloride acting on the aluminium chloride with phosgene, converting thereby the aluminium chloride into a liquid double compound, acting on the said double compound with an oxidizing agent, separat- 'ing the said liquid double compound from undissolved iron compounds and recovering aluminium chloride by evaporating off the phosgene.

4. A process for the purification of anhydrous aluminium chloride containing iron compounds comprising ferric chloride which comprises reducing the ferric chloride present to ferrous chloride by the addition of a metal capable of reducing ferric chloride to ferrous chloride, acting on the aluminium chloride with phosgene, converting thereby the aluminium chloride into a liquid double compound, acting on the double compound with an oxidizing agent, separating the said liquid double compound from undissolved iron compounds and recovering aluminium chloride by evaporating off the phosgene.

5. A aroccss for the purification of anhydrous a luminium chloride containing iron compounds comprising ferric chloride which comprises reducing'the ferric chloride present to ferrous chloride by the addition of aluminium, acting on the aluminium chloride with phosgene, converting thereby the aluminium chloride into a liquid double compound, acting on the double compound with an oxidizing agent, separating the said liquid double compound from undissolved iron compounds and recovering aluminium chloride by evaporating off the phosgene.

6. A process for the purification of anhydrous aluminium chloride containing iron compounds comprising ferric chloride which comprises reducing the ferric chloride present to ferrous chloride by the addition of aluminium, acting on the aluminium chloride with phosgene, converting thereby the aluminium chloride into a liquid double compound, acting on the said double compound with chlorine, separating the said compound from undissolved iron compounds and recovering aluminium chloride by evaporating off the phosgene.

In testimony whereof we have hereunto set our hands.

CARL WINTER. NIKOLAUS ROH. 

